Docket Number EPA-HQ-OPP-2014-0279 

www.regulations.gov 

Imazapic Final Work Plan 

Registration Review 

Case Number 7234 

March 2015 

Approved by: ~~P~,p 

Date: 

Richard P. Keigwin, Jr. 

Director 

Pesticide Re-evaluation Division 
INTRODUCTION 

This is the Environmental Protection Agency's (EPA or the Agency) Final Work Plan (FWP) for 

the registration review of imazapic and imazapic ammonium (imazapic). This work plan 

addresses public comments received concerning the Preliminary Work Plan (PWP), which was 

posted in the imazapic registration review docket (EPA-HQ-OPP-2014-0279). lmazapic is a 

systemic herbicide belonging to the imidazolinine class of pesticide, which share a common 

mechanism of action that involves the inhibition of acetolactate synthase (ALS) enzyme, an 

enzyme found in plants. [mazapic is registered to control certain grasses and broadleaf weeds on 

peanuts, grass (pasture and rangeland) and a wide range of non-crop areas including utility rightof-ways, airports, turf, and recreational (non-residential) sites. 

The Agency is implementing the registration review program pursuant to Section 3(g) of the 

Federal Insecticide, Fungicide, and Rodenticide Act (FIFRA), and will review each registered 

pesticide every 15 years to determine whether it continues to meet the FIFRA standard for 

registration. Changes in science, public policy, and pesticide use practices occur over time. The 

registration review program is intended to make sure that, as the ability to assess risk evolves and 

as policies and practices change, all registered pesticides continue to meet the statutory standard. 

The public phase of registration review begins when the initial docket is opened for each case. 

Information on this program is provided on the Agency's website. 1 

The FWP begins with any updates since the PWP was issued. Next is a summary of substantive 

comments received during the public comment period for the PWP concerning anticipated data 

needs, expected risk assessments, or the estimated timeline identified in the PWP, and a 

summary of the Agency's responses to those comments. This section is followed by registration 

review planned data needs, risk assessments expected to be conducted, and the projected 

registration review timeline for imazapic. Lastly, there is a discussion of next steps. 

UPDATES SINCE THE PWP WAS ISSUED 

There are no additional updates on imazapic since the PWP. 

SUMMARY OF COMMENTS AND AGENCY RESPONSES 

During the 60-day public comment period on the lmazapic Preliminary Work Plan, which 

opened on September 24, 2014 and closed on November 23, 2014, the Agency received two 

public comments. Comments were submitted by the FrFRA Endangered Species Task Force 

(FESTF) and the Center for Biological Diversity (CBD). The comments do not address the 

timeline or the data requirements described in the PWP, but do address the planned ecological 

risk assessments. In the PWP, EPA also solicited comments on the specific topics of 

environmental justice, water quality concerns, and trade irritants, but no comments or 

information were received on those issues. 

Summarized below are the public comments. The full comments in their entirety are located in 

the docket, EPA-HQ-OPP-2014-0279. 

1 http://www.epa.gov/oppsrrd I /registration_review/ 

2 
Comments submitted by FESTF in EPA-HQ-OPP-2014-0279-0012. 

I. Comment: FESTF noted the availability of data to inform the Agency's endangered species 

assessment, and identified the FESTF members entitled to rely on FESTF data. 

Response: The Agency thanks FESTF for its comment and will consider this information 

during the imazapic registration review. 

Comments submitted by CBD in EPA-HQ-OPP-2014-0279-0013. 

3. Comment: CBD's comments focus on EPA's duty to consult with the U.S. Fish and Wildlife 

Service and the National Marine Fisheries Service (the Services) on the registration review of 

imazapic in accordance with the Endangered Species Act (ESA). CBD's comments mention 

various aspects of the risk assessment process, including use of the best available data to 

develop endangered species risk assessments, and evaluation of effects on endangered and 

threatened species and their designated critical habitat. 

Response: EPA has reviewed the comments from CBD on the registration review docket 

opening for imazapic and plans to address many of the concerns raised by CBD as part of the 

implementation plan for assessing the risks of pesticides to listed species based on the 

recommendations of the April 2013 National Academy of Sciences (NAS) report. EPA will 

address concerns specific to imazapic in connection with the development of its final 

registration review decision for this pesticide. 

In November 2013, the EPA, along with the Services and the USDA, released a summary of 

their joint Interim Approaches for assessing risks to endangered and threatened (listed) 

species from pesticides. The Interim Approaches were developed jointly by the agencies in 

response to the NAS recommendations and reflect a common approach to risk assessment 

shared by the agencies as a way of addressing scientific differences between the EPA and the 

Services. The NAS report outlines recommendations on specific scientific and technical 

issues related to the development of pesticide risk assessments that EPA and the Services 

must conduct in connection with their obligations under the ESA and FIFRA. 

The joint Interim Approaches were released prior to a stakeholder workshop held on 

November 15, 2013. In addition, the EPA presented the joint Interim Approaches at the 

December 2013 Pesticide Program Dialogue Committee (PPDC) and State-FIFRA Issues 

Research and Evaluation Group (SFIREG) meetings. The agencies also held a stakeholder 

workshop in Apri 1 2014 and October 2014, allowing additional opportunities for stakeholders 

to comment on the Interim Approaches. Additional workshops are planned to enhance 

stakeholder involvement; the next workshop is scheduled for April 2015. As part of a phased, 

iterative process for developing the Interim Approaches, the agencies will also consider public 

comments on the Interim Approaches in connection with the development of upcoming 

registration review decisions. The details of the joint Interim Approaches are contained in the 

white paper, Interim Approaches for National-Level Pesticide Endangered Species Act 

Assessments Based on the Recommendations of the National Academy of Sciences April 2013 

Report, dated November I, 2013. 

3 
Given that the agencies are continuing to develop and work toward implementation of the 

Interim Approaches to assess the potential risks of pesticides to listed species and their 

designated critical habitat, the ecological problem formulation supporting this Final Work 

Plan for imazapic does not describe the specific ESA analysis, including effects 

determinations for specific listed species or designated critical habitat, to be conducted during 

registration review. In the ecological problem formulation document for imazapic, EPA 

described the screening-level risk assessment to determine the potential effects of imazapic on 

all taxa of non-target wildlife and plants, which will assume that listed species and their 

designated critical habitats may be present in the vicinity of the application of imazapic. This 

screening-level assessment will allow EPA to focus its future evaluations on the types of 

species where the potential for effects exists once the scientific methods being developed by 

the agencies have been fully vetted. While the agencies continue to develop a common 

method for ESA analysis, the planned screening-level risk assessment for the registration 

review of imazapic will describe the level of ESA analysis completed for this particular 

registration review case. Once the agencies have fully developed and implemented the 

scientific methods necessary to complete risk assessments for endangered and threatened 

(listed) species and their designated critical habitats, these methods will be applied to 

subsequent analyses for imazapic as part of completing this registration review. 

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PLANNED DATA NEEDS 

Table I below summarizes the planned data needs for imazapic based on the Problem 

Formulation for Ecological Risk and Environmental Fate, Endangered Species, and Drinking 

Water Assessments/or lmazapic and its Ammonium Salt. The planned data needs have not 

changed from what was included in the PWP. 

Table 1: Anticipated Data Needs for the Imazapic Registration Review 

Estimated 

Guideline Study Title2 Timeframe 

Number2 Test Material (Months from 

receipt ofDCI) 

830.6317 Storage Stability (soil) TGAI 12 

835.4100 Aerobic Soil Metabolism3 TGAI 24 

835.4200 Anaerobic Soil Metabolism TGAI 24 

835.4300 Aerobic Aquatic Metabolism TGAI 24 

850.2100 Avian Acute Oral Toxicity Test4 TGAI 12 

Non- Honey Bee Adult Acute Oral Toxicity5 TGAI 12 

guideline 

Non- Honey Bee Adult Chronic Oral Toxicity5 TGAI 12 

guideline 

Non- Honey Bee Larvae Acute Oral Toxicity5 TGAI 12 guideline 

Non- Honey Bee Larvae Chronic Oral Toxicity5 TGAI 12 guideline 

Non- Semi-Field Testing for Pollinators5

• 

6 TEP 24 

guideline 

Non- Measur~ of Residues in Pollen and Nectar5

• 

6 TEP 24 

guideline 

850.3040 Field Testing for Pollinators5

• 

6 TEP 24 

850.4100 Seedling Emergence and Seedling Growth7 TEP 12 

850.4150 Vegetative Vigor TEP 12 

Environmental Chemistry Methods and 

850.6100 Associated Independent Laboratory TGAl 12 

Validations for Soil and Water 

TGAJ =technical grade active ingredient; TEP =typical end-use product; 

2 On June 27, 2012, EPA announced certain revisions in harmonized guideline series 850 - Ecological Effects Tests 

- including renumbering and other designations or changes for some guideline studies. See "Final Test 

Guidelines; OCSPP 850 Series; Notice of Availability" 77 FR 38282, June 27, 20 12. 

http://www.regulations.gov/#! documentDetai I; D=EPA-H0-0PPT-2009-0154-0028 3 Need three additional soils. 4 Conducted with a passerine species. 

5 A protocol should be submitted to the Agency for review prior to study initiation. 

6 The need for this test may be waived pending the results of the requested lower tier pollinator tests. 

7 Data is requested for tomato, oats and ryegrass. 

5 
In addition to the data needs listed in Table l, the Problem Formulation identified the utility of 

an additional study which could improve the accuracy of risk estimations for imazapic. Data on 

the toxicity of imazapic's degradates to aquatic vascular plants from aquatic photolysis 

(Guideline 850.4400, Aquatic Plant Toxicity Test Using Lemna spp.) would help better 

characterize risk to this taxa. Currently the Agency plans to estimate the toxicity of residues to 

aquatic organisms utilizing the Total Toxic Residues (TTR) approach which assumes degradates 

are equally toxic as the parent Registrants are encouraged to submit the relevant data within the 

data submission timeframe identified in the Projected Registration Review Timeline (see Table 

3). 

RISK ASSESSMENTS FOR REGISTRATION REVIEW 

During registration review, the Agency will conduct a comprehensive ecological risk assessment, 

including an endangered species assessment, for all uses of imazapic. EPA anticipates the need 

to conduct revised dietary, residential and occupational, and aggregate risk assessments during 

registration review. If toxicological endpoints or points of departure are revised based on the 

data that are anticipated to be required for registration review, they will be considered in the new 

assessments. In addition, any changes to the standard operating procedures (SOPs) or default 

exposure assumptions will also be reflected in the assessments for registration review. 

Table 2 below summarizes the planned registration review risk assessments based on the EFED 

Problem Formulation and HED Scoping Document. The planned assessments have not changed 

from what was included in the PWP. 

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Table 2: Planned Risk Assessments for the Imazapic Registration Review 

Type of Risk Assessment Conduct? Notes 

Ecologfoal and Environmental Fate 

Comprehensive ecological y EFED will conservatively characterize this risk by 

assessment, including utilizing a TTR approach. In this approach, a single 

endangered species (includes exposure concentration is estimated for total residues 

terrestrial and aquatic (i.e. parent imazapic and the five degradates identified 

organisms) in the aqueous photolysis study) and compared to a 

representative toxicity endpoint for the parent (i.e. 

assumes equal toxicity of each degradate to parent 

imazapic) 

Incidents Will check for For a discussion of reported ecological incidents for 

updates imazapic, see page 22 of the EFED Problem 

Formulation document. 

Human Health 

Dietary 

Food y Acute oral endpoints could not be identified, and as a 

result an acute dietary exposure assessment will not 

be conducted. In the most recent risk assessment done 

in 2013, chronic dietary exposures were not of 

concern to HED. 

Drinking water y A revised dietary exposure analysis may be required 

to reflect the most recent dietary exposure models and 

potential revised estimated drinking water 

concentrations. 

Occupational 

Handlers (mixers, loaders, y Occupational handler inhalation exposure assessments 

applicators) need to be performed for the scenarios that have not 

been previously assessed. 

Post-application y The need for a quantitative occupational postapplication inhalation exposure assessment will be 

considered during registration review. 

Residential 

Handlers y The residential handler assessment may need to be 

revised based on new residential handler SOP's and 

policy changes for body weights and toxicological 

endpoints. 

Post-application N Residential post-application assessments do not need 

to be performed as imazapic label directions indicate 

the turf use is specific to spot treatment only. 

Other 

Aggregate y A new aggregate risk assessment may be required 

during Registration Review to incorporate any revised 

dietary exposure analyses and/or residential exposure 

assessments. 

7 
Cumulative N EPA has not made a common mechanism of toxicity 

finding for imazapic and any other substances. 

Tolerances N No data is needed to support current tolerances for 

imazapic. There are no maximum residue limits 

(MRLs) in Canada or Mexico for imazapic. MRL 

definitions differ between U.S. and Codex, and will 

be evaluated during registration review. 

Incidents Will check for For a discussion of reported human incidents for 

updates imazapic, see page l 0 of the Scoping Document and 

the lmazapic and lmazapic Ammonium: Tier I Review 

of Human Incidents. 

TIME LINE 

EPA has created the following estimated timeline for the completion of the imazapic registration 

review in Table 3 below. The projected timeline has not changed since the PWP. 

Table 3: Registration Review for Imazapic - Projected Registration Review Timeline 

Activities Estimated Date 

Opening the Docket 

Open Docket and 60-day Public Comment Period September 2014 - Completed 

Close Public Comment November 2014 - Completed 

Case Development 

Final Work Plan March 2015 - Completed 

Issue DCI April - June 2015 

Data Submission April - June 2017 

60-day Public Comment Period for Draft Risk October - December 2018 

Assessments8 

Registration Review Decision 

60-day Public Comment Period for Proposed April - June 2019 

Registration Review Decision 

Registration Review Decision and Begin Post-Decision 2019 

Follow-up 

Total (years) 5 

NEXT STEPS 

As noted previously, the Agency plans to require several environmental fate, ecological effects, 

and human health studies for imazapic through a Data Call-In Notice, expected to be issued by 

June 2015. 

8 The regulations governing Registration Review generally require the Agency to provide a public comment period 

of at least 30 calendar days for draft risk assessments; see 40 CFR Part J 55.53(c). For conventional pesticides, the 

Agency plans to provide a 60 calendar day public comment period generally for draft risk assessments. 

8